As is known in the art, the existence of foreign matter or objects (e.g., mud or snow) on a radar such as an automotive radar sensor of the type described in U.S. Pat. No. 5,959,570 can impact the accuracy and reliability of the radar. For example, the foreign matter or objects may undesirably block one or more portions of the radar sensor transmit and/or receive antennas and in particular may block portions of the RF energy propagating to and from the transmit and receive antennas of the radar sensor.
Such blockage may, for example, be the result of an accumulation, over a period of time, of foreign matter or objects in the region of an antenna aperture. Such foreign matter may be caused for example by environmental conditions such as temperature, humidity, ice, rain, and the like. Such blockage can degrade, or in extreme cases even prevent, proper operation of the automotive radar sensor. For example, blockages can result in reduction of signal strength and/or distortion of target angles. If the foreign matter accumulates over time, there is a corresponding gradual decrease in sensor system performance over time. Since the accumulation is gradual, it is sometimes relatively difficult to detect the existence of antenna blockage due to the gradual accumulation of foreign matter and corresponding gradual decrease in radar sensor performance.
As is also known, some prior attempts to detect radar blockage include analyzing statistics from passing objects (e.g., passing vehicles). Examples of systems and methods for blockage detection utilizing statistics related to passing objects to can be found in U.S. Pat. No. 7,973,701.